On Fri, 2013-07-12 at 19:04 +0200, Hervé Poussineau wrote: > "When PowerPC little-endian is in effect but before system's > little-endian is in effect, the address munge becomes effective. If we > need to access system endian port (byte) address, say 0x80000092, the > program needs to issue 0x80000095 instead, to compensate (unmunge) for > the effect of PowerPC address modification." > > Those will be required for QEMU to be able to run BeOS, AIX, or Windows > NT or PowerPC PReP.
Funnily enough we've dropped support for Linux on PReP a long time ago :-) > In the light of this, I think there should only be one endianness for > all memory accesses (which could be changed at runtime), and all > bridges/devices should ask for "same endianness as parent" or "reverse > endianness as parent", but not for big, little, or native endianness. Right. I would in fact avoid the term "endianness" that tends to confuse people and basically stick to this: - For a given access, know (attribute) which byte is first in ascending address order - For a given target *register* (and again, this ONLY applies to registers and in fact, some devices might change their register "endianness" and also have several banks with a different one), which byte is first in ascending address order. This is at that point that a conversion might need to occur, and only at that point if there is a mismatch. Ben.
